Typical methods for recognizing the position and attitude of a recognition object in an image to be processed through two-dimensional image processing include a method that acquires correlation values between a pre-registered model image and the image to be processed (see, e.g., Patent Document 1). In addition, there is also a case in which the three-dimensional coordinates of a plurality of feature points of a recognition object are calculated by means of three-dimensional measurement processing using a stereo camera, followed by calculation of obtaining correlation values between a distribution pattern of these feature points and a distribution pattern of feature points of a model in a three-dimensional space, thereby recognizing the position and attitude of the recognition object in the space (see, e.g., Patent Document 2).
Patent Document 1: Japanese Patent Application Laid-Open No. 2005-346232
Patent Document 2: Japanese Patent Application Laid-Open No. 2004-295223
In the two-dimensional image processing, in addition to being different in position and orientation from the model, a recognition object is sometimes changed in the size in its image due to variation in distance between the camera and recognition objects. Thus, in order to accurately recognize an object to be measured that is in a different condition from the model image, conventionally, a plurality of kinds of model images that are different in orientation and size from one another are typically registered, and correlation values are calculated per model image. According to such a method, however, the more the number of matching operations with the model images, the longer the time taken for the processing.
The three-dimensional recognition processing involves repetition of the process of varying the positions and directions of the feature points of the model to acquire the correlation values with respect to feature points of a recognition object. In this case also, the more diverse the position-direction combinations of the feature points of the model, the longer the time taken for the processing.
As described above, both in the two-dimensional and three-dimensional processing, processing time becomes longer to achieve a high degree of recognition accuracy. As this kind of recognition processing is performed as pre-processing for a measurement or an inspection in many cases, it is not desirable to take much time for the processing.
The present invention was made in view of the foregoing problems, and it is an object of the invention to finish processing in a predetermined period of time while maintaining a certain degree of recognition accuracy.